Where does the heat come from in a commercial airplane engine?
The heat comes from two sources: 1) Compression: The air that a jet engine sucks in is compressed in the intake portion of the engine. Compression is a heating process because all the heat energy in the massive amount of air sucked in is compressed into a much smaller volume. (If you’ve ever sprayed an aerosol can and felt it get cold, it’s the same thing but in reverse.) 2) Combustion: Some of the compressed air is mixed with fuel and burned. The burning produces heat. In a typical jumbo jet engine, the temperature reaches around 900 degrees Fahrenheit just from compression. The combustion mixture is immediately allowed to expand, so it actually tends to be around the same temperature (except right at the point where it’s burning where it can reach over 3,000 degrees Fahrenheit).
